I would ask a different question. You are obviously working out, and I assume that you have a balanced workout. So, in theory, there should not be any difference between the sides.
If, as you say, there is, then there must be a different reason, and I suspect this to be postural, possibly work-related. The left trap may appear bigger because you may be in the habit of raising your shoulder all the time. That could make the left lat look smaller than the right.
My suggestion is to take a look at this first before you begin with changes in unilateral exercises. This may only exacerbate the problem.